Field of the Invention
The present invention is broadly concerned with high efficiency material processing equipment making use of one or more inverting pan conveyors which make maximal use of both the upper and lower runs of the conveyors. More particularly, the invention is concerned with such equipment, the individual conveyors thereof, the pans forming a part of the conveyors, and corresponding methods. The apparatus and methods of the invention are particularly useful for the processing of cut extrudate materials, such as extruded feed or food products.
Description of the Prior Art
Conventional multiple-stage product dryers and coolers typically include a series of endless, stacked conveyors within a housing and oriented so that incoming material is placed on the uppermost conveyor, which then feeds the succeeding lower conveyors. Apparatus is provided for directing air into the dryer housing for drying or cooling of the material as it is conveyed along and between the conveyors. Each conveyor includes an upper run and a lower run, but, in these conventional units, only the upper runs are used for material conditioning, with the lower runs essentially being idlers. This entails a double expenditure of materials used in the construction of the equipment and excess power requirements during operation thereof.
In response to these problems, so-called inverting pan conveyors have been provided. In these units, the conveyors utilize both the upper and lower runs thereof during material processing. That is, the conveyors are designed to transfer materials from the upper to the lower runs thereof so as to increase processing efficiencies. However, in most instances, these prior inverting pan conveyors require dumping or short-circuiting of product from the upper run to the lower run at an intermediate position between the terminal sprockets supporting the conveyors, thereby sacrificing processing efficiency.
For example, U.S. Pat. Nos. 1,768,534 and 1,568,791 to Aiken describe inverting pan conveyors where product is introduced onto the conveyor pans adjacent one end of the upper run, with a cam arrangement to tilt the pans downwardly to transfer product to the lower run well before the opposite terminal sprocket is reached. Similarly, as the product traverses the lower run, it is dumped to a succeeding lower conveyor at a substantial distance from the opposite end sprockets. To a similar effect is U.S. Pat. No. 4,366,628 to George, wherein (FIG. 1) product is delivered from a chute 36 to the upper run, and is then delivered to the lower run at a substantial distance before the terminal sprocket 14 is reached. Other patents having similar design features include U.S. Pat. No. 1,328,099 to Parker, U.S. Pat. No. 538,728 to Davidson, U.S. Pat. No. 3,331,490 to Daniels, GB Patent No. 358,493 to Sutton, GB Patent No. 1,109,752 to Williams, French Patent No. FR 944,968 to Piscaglia, German reference DE 3,006,126 to Lindner, and the non-patent literature entitled “Pan Conveyors,” found online at http://www.aumund.com/content/pdf/pageflip/21413457/pan_conveyors_engl_141215.pdf (Accessed Oct. 8, 2015).
U.S. Pat. No. 1,344,893 to Hofmann illustrates a conveyor design (see FIGS. 5, 7, and 8) wherein short pans move between the terminal sprockets and dump product as the pans traverse the sprockets. In this design, the individual pans are mounted so that they pivot relative to the sprockets as they go around the sprockets. This is inherently a complicated design with a complex mechanical arrangement for controlling the movements of the pans.
There is accordingly a need in the art for improved inverting pan conveyors that overcome the problems outlined above and provide a simplified, efficient conveyor arrangement which can be used in product dryers and the like.